U.S. patent application number 12/062577 was filed with the patent office on 2008-10-09 for high speed, high density electrical connector with selective positioning of lossy regions.
Invention is credited to Thomas S. Cohen, Brian Kirk.
Application Number | 20080248660 12/062577 |
Document ID | / |
Family ID | 39827333 |
Filed Date | 2008-10-09 |
United States Patent
Application |
20080248660 |
Kind Code |
A1 |
Kirk; Brian ; et
al. |
October 9, 2008 |
HIGH SPEED, HIGH DENSITY ELECTRICAL CONNECTOR WITH SELECTIVE
POSITIONING OF LOSSY REGIONS
Abstract
An electrical interconnection system with high speed, high
density electrical connectors. The connectors incorporate
electrically lossy material, selectively positioned to reduce
crosstalk without undesirably attenuating signals. The lossy
material may be molded through ground conductors that separate
adjacent differential pairs within columns of conductive elements
in the connector. However, regions of lossy material may be set
back from the edges of the ground conductors to avoid undesired
attenuation of signals. Also, the lossy material may be positioned
in multiple regions along the length of signal conductors. The
regions may be separated by holes, notches, gaps or other openings
in the lossy material, which can be simply formed as part of a
molding operation.
Inventors: |
Kirk; Brian; (Amherst,
NH) ; Cohen; Thomas S.; (New Boston, NH) |
Correspondence
Address: |
WOLF GREENFIELD & SACKS, P.C.
600 ATLANTIC AVENUE
BOSTON
MA
02210-2206
US
|
Family ID: |
39827333 |
Appl. No.: |
12/062577 |
Filed: |
April 4, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60921740 |
Apr 4, 2007 |
|
|
|
Current U.S.
Class: |
439/68 |
Current CPC
Class: |
H01R 13/6477 20130101;
H01R 13/514 20130101; H01R 12/724 20130101; H01R 12/52 20130101;
H01R 13/6599 20130101; H01R 23/688 20130101 |
Class at
Publication: |
439/68 |
International
Class: |
H01R 12/14 20060101
H01R012/14 |
Claims
1. An electrical connector comprising: a) a plurality of signal
conductors, the plurality of signal conductors being disposed in an
array; and b) a housing comprising: i) at least one insulative
member disposed to hold the plurality of signal conductors in the
array; and ii) at least one lossy member disposed along a length of
a signal conductor to provide a plurality of lossy regions between
the signal conductor and an adjacent signal conductor with at least
one insulative region between adjacent lossy regions.
2. The electrical connector of claim 1, wherein the lossy regions
and the at least one insulative region are adapted and arranged to
reduce crosstalk between the signal conductor and the adjacent
signal conductor with limited loss of signals carried by the signal
conductor and adjacent signal conductor.
3. The electrical connector of claim 1, wherein the at least one
insulative member comprises molded plastic and the at least one
lossy member comprises molded plastic having conductive
fillers.
4. The electrical connector of claim 1, wherein the at least one
insulative member comprises molded plastic and the at least one
lossy member comprises a plating on a surface of molded plastic
that has lossy characteristics over a frequency range of 1 GHz to
12 GHz.
5. The electrical connector of claim 1, wherein the plurality of
signal conductors are adapted and arranged to form a plurality of
differential pairs and the plurality of lossy regions are disposed
between adjacent signal conductors that form members of separate
differential signal pairs.
6. The electrical connector of claim 1, wherein: the plurality of
signal conductors are arranged in a column; the at least one lossy
member comprises a parallel region parallel to the column and a
plurality of perpendicular regions, extending from the parallel
region; and the at least one insulative region comprises at least
one opening in the parallel region between adjacent perpendicular
regions.
7. The electrical connector of claim 6, wherein: the other
plurality of signal conductors in the column comprises a plurality
of differential pairs, each pair having a first and a second signal
conductor; each of the plurality of perpendicular regions is
disposed between an adjacent differential pair; and the at least
one opening in the parallel region comprises at least one opening
positioned between the first and second signal conductors of a
pair.
8. The electrical connector of claim 7, wherein the at least one
insulative region further comprises at least one opening in the
perpendicular regions.
9. The electrical connector of claim 8, wherein: the at least one
opening in the parallel region comprises an opening in the parallel
region between each adjacent perpendicular region; and the at least
one opening in the perpendicular regions comprises an opening in
each of the perpendicular regions, each opening in the
perpendicular region in communication with an opening of the at
least one opening in the parallel region, whereby each of the
plurality of lossy regions comprises a U-shaped segment comprising
a portion of the parallel region and a portion of the perpendicular
regions and the plurality of lossy regions are separated by the
openings in the perpendicular regions and the parallel regions.
10. The electrical connector of claim 1, wherein: the plurality of
signal conductors is arranged in a column; the at least one lossy
member comprises a parallel region parallel to the column and a
plurality of perpendicular regions, extending from the parallel
region; and the at least one insulative region comprises at least
one opening in at least one region of the plurality of
perpendicular regions.
11. The electrical connector of claim 1, wherein: the plurality of
signal conductors are disposed in a column comprising a plurality
of differential pairs; the at least one lossy member forms a
plurality of channels having a bottom defined by a parallel region
and sides defined by adjacent perpendicular regions extending from
the parallel region, each of the channels receiving a differential
pair; and each of the plurality of lossy regions comprises a
portion of at least one of the plurality of channels separated by
openings in the perpendicular regions.
12. The electrical connector of claim 1, wherein the at least one
insulative region comprises air and/or a portion of the at least
one insulative member.
13. The electrical connector of claim 1, wherein: each signal
conductor comprises a mating contact portion, a contact tail and an
intermediate portion electrically coupling the mating contact
portion to the contact tail, and the intermediate portion of each
signal conductor is embedded in the at least one insulative member;
the plurality of signal conductors are arranged in a plurality of
columns, the plurality of signal conductors in each of the
plurality of columns comprising a plurality of differential pairs;
the at least one lossy member comprises a plurality of parallel
regions and a plurality of perpendicular regions, each of the
plurality of parallel regions being disposed parallel to a column
of the plurality of columns and each of the plurality of
perpendicular regions extending from a parallel region; the at
least one insulative region comprises at least one opening in each
of the plurality of parallel regions between adjacent perpendicular
regions; the at least one lossy member comprises a lossy member
adjacent each of the plurality of columns, each lossy member
forming a plurality of channels having a bottom defined by the
parallel region adjacent the column and sides defined by adjacent
perpendicular regions, each of the channels receiving a
differential pair and each of the plurality of lossy regions
comprises a portion of at least one of the plurality of channels
separated by the openings in the lossy member; each of the
plurality of perpendicular regions being disposed between an
adjacent differential pair within a column of the plurality of
columns; and the lossy regions and the insulative regions are
adapted and arranged to reduce crosstalk between adjacent pairs of
signal conductors with limited loss to signals carried by the pairs
of the adjacent pairs of signal conductors.
14. The electrical connector of claim 13, further comprising a
plurality of ground conductors, each of the ground conductors
electrically connected to a perpendicular region of the plurality
of perpendicular regions.
15. The electrical connector of claim 13, wherein each of the
differential pairs in a column has a different length and the lossy
regions are sized and arranged to provide a higher loss per unit
length to shorter differential pairs than to longer differential
pairs.
16. An electrical connector comprising: a) a plurality of signal
conductors, the plurality of signal conductors being disposed in an
array having at least one column; b) a housing comprising a
plurality of lossy regions, each lossy region disposed adjacent at
least one of the plurality of signal conductors; and c) a plurality
of ground conductors, each of the ground conductors: being disposed
in a column of the at least one column; being disposed adjacent at
least one signal conductor of the plurality of signal conductors in
the column; and having at least one edge facing the at least one
adjacent signal conductor; and wherein lossy regions of the
plurality of lossy regions are positioned relative to ground
conductors of the plurality of ground conductors with a setback
from the edge of the ground conductor in a direction away from the
signal conductor adjacent the ground conductor.
17. The electrical connector of claim 16, further comprising at
least one insulative portion, the insulative portion having a
plurality of insulative regions; and wherein for each ground
conductor, an insulative region of the plurality of insulative
regions is positioned between an adjacent signal conductor and a
lossy region adjacent the signal conductor and the insulative
region is positioned in the setback.
18. The electrical connector of claim 17, wherein the insulative
portion comprises molded plastic and is adapted and arranged to
hold the plurality of signal conductors in an array.
19. The electrical connector of claim 17, wherein the insulative
portion comprises a region of air.
20. An electrical connector comprising: a) a plurality of signal
conductors, the plurality of signal conductors being disposed in an
array having at least one column; b) a housing comprising a
plurality of lossy regions, each lossy region adjacent at least one
of the plurality of signal conductors; and c) a plurality of ground
conductors, each of the ground conductors having an opening
therethrough, and each of the ground conductors being disposed in a
column of the at least one column, and each of the ground
conductors being in electrical connection with a lossy region of
the plurality of lossy regions; wherein a portion of the lossy
region in electrical connection with each ground conductor is
disposed through the opening in the ground conductor.
21. The electrical connector of claim 20, wherein i) each of the
ground conductors is disposed adjacent a signal conductor in the
column; ii) each of the ground conductors has an edge facing the
adjacent signal conductor, iii) the lossy region in electrical
connection with the ground conductor is disposed with a setback
from the edge.
22. The electrical connector of claim 20, wherein: i) the
electrical connector comprises a plurality of subassemblies, each
subassembly having a first side and a second side, and the
subassemblies being aligned side-by-side; ii) the at least one
column comprises a plurality of columns, each column being
positioned in a separate one of the plurality of subassemblies; and
iii) in each subassembly a lossy region is exposed in a first side
and at least one of the portions of the lossy region is
electrically coupled to the second side.
23. The electrical connector of claim 22, wherein in each
subassembly, at least one of the portions is exposed in the second
side.
24. The electrical connector of claim 23, wherein the plurality of
subassemblies are positioned to electrically couple the lossy
regions of the plurality of subassemblies together, the coupling
being formed by lossy regions exposed in the first sides of
subassemblies of the plurality of subassemblies coupled to lossy
regions exposed in the second sides of subassemblies of the
plurality of subassemblies.
25. The electrical connector of claim 22, wherein in each
subassembly a conductor exposed in the second side is electrically
connected to at least one of the portions.
26. An electrical connector comprising: a) a plurality of signal
conductors, the plurality of signal conductors being disposed in an
array having a plurality of columns; b) a plurality of ground
conductors, each of the ground conductors being disposed in a
column of the plurality of columns; and c) a housing comprising a
plurality of lossy regions, wherein the lossy regions are
positioned: i) between two adjacent columns in regions between two
adjacent signal conductors, each of the two adjacent signal
conductors being in a different one of the two adjacent columns;
and ii) between two adjacent ground conductors, each of the two
adjacent ground conductors being in one of the two adjacent
columns.
27. The electrical connector of claim 26, wherein: i) the plurality
of signal conductors comprises a plurality of differential pairs
with the ground conductors of the plurality of ground conductors
disposed between adjacent differential pairs; and ii) lossy regions
are disposed between two adjacent differential pairs, each adjacent
differential pair being in a different one of the two adjacent
columns.
28. The electrical connector of claim 26, wherein each lossy region
is electrically connected to at least one of the two adjacent
ground conductors.
29. The electrical connector of claim 26, wherein the housing
comprises a plurality of subassemblies, each subassembly having an
insulative portion holding a column of signal conductors.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application 60/921,740, filed Apr. 4, 2007 and incorporated herein
by reference.
BACKGROUND OF INVENTION
[0002] 1. Field of Invention
[0003] This invention relates generally to electrical
interconnection systems and more specifically to improved signal
integrity in interconnection systems, particularly in high speed
electrical connectors.
[0004] 2. Discussion of Related Art
[0005] Electrical connectors are used in many electronic systems.
It is generally easier and more cost effective to manufacture a
system on several printed circuit boards ("PCBs") that are
connected to one another by electrical connectors than to
manufacture a system as a single assembly. A traditional
arrangement for interconnecting several PCBs is to have one PCB
serve as a backplane. Other PCBs, which are called daughter boards
or daughter cards, are then connected through the backplane by
electrical connectors.
[0006] Electronic systems have generally become smaller, faster and
functionally more complex. These changes mean that the number of
circuits in a given area of an electronic system, along with the
frequencies at which the circuits operate, have increased
significantly in recent years. Current systems pass more data
between printed circuit boards and require electrical connectors
that are electrically capable of handling more data at higher
speeds than connectors of even a few years ago.
[0007] One of the difficulties in making a high density, high speed
connector is that electrical conductors in the connector can be so
close that there can be electrical interference between adjacent
signal conductors. To reduce interference, and to otherwise provide
desirable electrical properties, metal members are often placed
between or around adjacent signal conductors. The metal acts as a
shield to prevent signals carried on one conductor from creating
"crosstalk" on another conductor. The metal also impacts the
impedance of each conductor, which can further contribute to
desirable electrical properties.
[0008] As signal frequencies increase, there is a greater
possibility of electrical noise being generated in the connector in
forms such as reflections, crosstalk and electromagnetic radiation.
Therefore, the electrical connectors are designed to limit
crosstalk between different signal paths and to control the
characteristic impedance of each signal path. Shield members are
often placed adjacent the signal conductors for this purpose.
[0009] Crosstalk between different signal paths through a connector
can be limited by arranging the various signal paths so that they
are spaced further from each other and nearer to a shield, such as
a grounded plate. Thus, the different signal paths tend to
electromagnetically couple more to the shield and less with each
other. For a given level of crosstalk, the signal paths can be
placed closer together when sufficient electromagnetic coupling to
the ground conductors is maintained.
[0010] Although shields for isolating conductors from one another
are typically made from metal components, U.S. Pat. No. 6,709,294
(the '294 patent), which is assigned to the same assignee as the
present application and which is hereby incorporated by reference
in its entirety, describes making an extension of a shield plate in
a connector from conductive plastic.
[0011] Other techniques may be used to control the performance of a
connector. Transmitting signals differentially can also reduce
crosstalk. Differential signals are carried on by a pair of
conducting paths, called a "differential pair." The voltage
difference between the conductive paths represents the signal. In
general, a differential pair is designed with preferential coupling
between the conducting paths of the pair. For example, the two
conducting paths of a differential pair may be arranged to run
closer to each other than to adjacent signal paths in the
connector. No shielding is desired between the conducting paths of
the pair, but shielding may be used between differential pairs.
Electrical connectors can be designed for differential signals as
well as for single-ended signals.
[0012] Examples of differential electrical connectors are shown in
U.S. Pat. No. 6,293,827, U.S. Pat. No. 6,503,103, U.S. Pat. No.
6,776,659, and U.S. Pat. No. 7,163,421, all of which are assigned
to the assignee of the present application and are hereby
incorporated by reference in their entireties.
[0013] Electrical characteristics of a connector may also be
controlled through the use of absorptive material. U.S. Pat. No.
6,786,771, (the '771 patent), which is assigned to the assignee of
the present application and which is hereby incorporated by
reference in its entirety, describes the use of absorptive material
to reduce unwanted resonances and improve connector performance,
particularly at high speeds (for example, signal frequencies of 1
GHz or greater, particularly above 3 GHz).
[0014] U.S. Published Application 2006/0068640, which is assigned
to the assignee of the present invention and which is hereby
incorporated by reference in its entirety, describes the use of
lossy material to improve connector performance.
SUMMARY OF INVENTION
[0015] An improved electrical connector is provided with selective
positioning of lossy regions. The lossy regions can reduce
crosstalk between adjacent signal conductors without producing an
undesirable amount of attenuation for signals carried by those
signal conductors. One technique for selectively positioning lossy
regions involves providing multiple segments of lossy material
separated by insulative regions along signal conductors. Another
technique involves positioning lossy regions in association with
ground conductors and positioning the lossy regions with a setback
from edges of the ground conductors. A further technique involves
positioning the lossy regions to extend through ground conductors.
A further technique involves positioning the lossy regions between
adjacent parallel columns of conductive elements in a volume that
is between both two ground conductors and two signal conductors in
adjacent columns. These techniques may be used singly or in
combination.
[0016] Accordingly, in one aspect, the invention relates to an
electrical connector comprising a plurality of signal conductors.
The plurality of signal conductors are disposed in an array. The
connector has a housing that comprises at least one insulative
member disposed to hold the plurality of signal conductors in the
array. The housing also includes at least one lossy member disposed
along a length of a signal conductor to provide a plurality of
lossy regions between the signal conductor and an adjacent signal
conductor with at least one insulative region between adjacent
lossy regions.
[0017] In another aspect, the invention relates to an electrical
connector comprising a plurality of signal conductors. The
plurality of signal conductors are disposed in an array having at
least one column. The connector has a housing comprising a
plurality of lossy regions. Each lossy region is disposed adjacent
at least one of the plurality of signal conductors. A plurality of
ground conductors in the connector are each disposed in a column of
the at least one column. Each ground conductor is disposed adjacent
at least one signal conductor of the plurality of signal conductors
in the column and has at least one edge facing the at least one
adjacent signal conductor. Lossy regions of the plurality of lossy
regions are positioned relative to ground conductors of the
plurality of ground conductors with a setback from the edge of the
ground conductor in a direction away from the signal conductor
adjacent the ground conductor.
[0018] In yet a further aspect, the invention relates to an
electrical connector comprising a plurality of signal conductors.
The plurality of signal conductors are disposed in an array having
at least one column. The connector has a housing comprising a
plurality of lossy regions. Each lossy region is adjacent at least
one of the plurality of signal conductors. A plurality of ground
conductors with the connector each has an opening therethrough.
Each of the ground conductors is disposed in a column of the at
least one column, and each of the ground conductors is in
electrical connection with a lossy region of the plurality of lossy
regions. A portion of the lossy region in electrical connection
with each ground conductor is disposed through the opening in the
ground conductor.
[0019] In yet a further aspect, the invention relates to an
electrical connector comprising a plurality of signal conductors.
The plurality of signal conductors is disposed in an array having a
plurality of columns. The connector also has a plurality of ground
conductors, each disposed in a column of the plurality of columns.
A housing for the connector comprises a plurality of lossy regions.
The lossy regions are positioned: i) between two adjacent columns
in regions between two adjacent signal conductors, each of the two
adjacent signal conductors being in a different one of the two
adjacent columns; and ii) between two adjacent ground conductors,
each of the two adjacent ground conductors being in one of the two
adjacent columns.
BRIEF DESCRIPTION OF DRAWINGS
[0020] The accompanying drawings are not intended to be drawn to
scale. In the drawings, each identical or nearly identical
component that is illustrated in various figures is represented by
a like numeral. For purposes of clarity, not every component may be
labeled in every drawing. In the drawings:
[0021] FIG. 1 is a perspective view of an electrical
interconnection system according to an embodiment of the present
invention;
[0022] FIGS. 2A and 2B are views of a first and second side of a
wafer forming a portion of the electrical connector of FIG. 1;
[0023] FIG. 2C is a cross-sectional representation of the wafer
illustrated in FIG. 2B taken along the line 2C-2C;
[0024] FIG. 3 is a cross-sectional representation of a plurality of
wafers stacked together according to an embodiment of the present
invention;
[0025] FIG. 4A is a plan view of a lead frame used in the
manufacture of a connector according to an embodiment of the
invention;
[0026] FIG. 4B is an enlarged detail view of the area encircled by
arrow 4B-4B in FIG. 4A;
[0027] FIG. 5A is a cross-sectional representation of a backplane
connector according to an embodiment of the present invention;
[0028] FIG. 5B is a cross-sectional representation of the backplane
connector illustrated in FIG. 5A taken along the line 5B-5B;
[0029] FIGS. 6A-6C are enlarged detail views of conductors used in
the manufacture of a backplane connector according to an embodiment
of the present invention;
[0030] FIG. 7A is a cross-sectional representation of two wafers
according to an embodiment of the present invention;
[0031] FIG. 7B is a schematic representation of two wafers
according to an embodiment of the present invention;
[0032] FIG. 8 is a cross-sectional representation of two wafers of
an electrical connector according to alternative embodiments of the
present invention;
[0033] FIGS. 9A-9C are cross-sectional representations of lossy
material portions of a wafer according to several embodiments of
the present invention; and
[0034] FIGS. 10A and 10B illustrate alternative embodiments of
lossy regions.
DETAILED DESCRIPTION
[0035] This invention is not limited in its application to the
details of construction and the arrangement of components set forth
in the following description or illustrated in the drawings. The
invention is capable of other embodiments and of being practiced or
of being carried out in various ways. Also, the phraseology and
terminology used herein is for the purpose of description and
should not be regarded as limiting. The use of "including,"
"comprising," "having," "containing," or "involving," and
variations thereof herein, is meant to encompass the items listed
thereafter and equivalents thereof as well as additional items.
[0036] Referring to FIG. 1, an electrical interconnection system
100 with two connectors is shown. The electrical interconnection
system 100 includes a daughter card connector 120 and a backplane
connector 150.
[0037] Daughter card connector 120 is designed to mate with
backplane connector 150, creating electronically conducting paths
between backplane 160 and daughter card 140. Though not expressly
shown, interconnection system 100 may interconnect multiple
daughter cards having similar daughter card connectors that mate to
similar backplane connections on backplane 160. Accordingly, the
number and type of subassemblies connected through an
interconnection system is not a limitation on the invention.
[0038] FIG. 1 shows an interconnection system using a right-angle,
backplane connector. It should be appreciated that in other
embodiments, the electrical interconnection system 100 may include
other types and combinations of connectors, as the invention may be
broadly applied in many types of electrical connectors, such as
right angle connectors, mezzanine connectors, card edge connectors
and chip sockets.
[0039] Backplane connector 150 and daughter connector 120 each
contains conductive elements. The conductive elements of daughter
card connector 120 are coupled to traces, of which trace 142 is
numbered, ground planes or other conductive elements within
daughter card 140. The traces carry electrical signals and the
ground planes provide reference levels for components on daughter
card 140. Ground planes may have voltages that are at earth ground
or positive or negative with respect to earth ground, as any
voltage level may act as a reference level.
[0040] Similarly, conductive elements in backplane connector 150
are coupled to traces, of which trace 162 is numbered, ground
planes or other conductive elements within backplane 160. When
daughter card connector 120 and backplane connector 150 mate,
conductive elements in the two connectors mate to complete
electrically conductive paths between the conductive elements
within backplane 160 and daughter card 140.
[0041] Backplane connector 150 includes a backplane shroud 158 and
a plurality conductive elements (see FIGS. 6A-6C). The conductive
elements of backplane connector 150 extend through floor 514 of the
backplane shroud 158 with portions both above and below floor 514.
Here, the portions of the conductive elements that extend above
floor 514 form mating contacts, shown collectively as mating
contact portions 154, which are adapted to mate to corresponding
conductive elements of daughter card connector 120. In the
illustrated embodiment, mating contacts 154 are in the form of
blades, although other suitable contact configurations may be
employed, as the present invention is not limited in this
regard.
[0042] Tail portions, shown collectively as contact tails 156, of
the conductive elements extend below the shroud floor 514 and are
adapted to be attached to backplane 160. Here, the tail portions
are in the form of a press fit, "eye of the needle" compliant
sections that fit within via holes, shown collectively as via holes
164, on backplane 160. However, other configurations are also
suitable, such as surface mount elements, spring contacts,
solderable pins, etc., as the present invention is not limited in
this regard.
[0043] In the embodiment illustrated, backplane shroud 158 is
molded from a dielectric material such as plastic or nylon.
Examples of suitable materials are liquid crystal polymer (LCP),
polyphenyline sulfide (PPS), high temperature nylon or
polypropylene (PPO). Other suitable materials may be employed, as
the present invention is not limited in this regard. All of these
are suitable for use as binder materials in manufacturing
connectors according to the invention. One or more fillers may be
included in some or all of the binder material used to form
backplane shroud 158 to control the electrical or mechanical
properties of backplane shroud 150. For example, thermoplastic PPS
filled to 30% by volume with glass fiber may be used to form shroud
158.
[0044] In the embodiment illustrated, backplane connector 150 is
manufactured by molding backplane shroud 158 with openings to
receive conductive elements. The conductive elements may be shaped
with barbs or other retention features that hold the conductive
elements in place when inserted in the opening of backplane shroud
158.
[0045] As shown in FIG. 1 and FIG. 5A, the backplane shroud 158
further includes side walls 512 that extend along the length of
opposing sides of the backplane shroud 158. The side walls 512
include grooves 172, which run vertically along an inner surface of
the side walls 512. Grooves 172 serve to guide front housing 130 of
daughter card connector 120 via mating projections 132 into the
appropriate position in shroud 158.
[0046] Daughter card connector 120 includes a plurality of wafers
122.sub.1 . . . 122.sub.6 coupled together, with each of the
plurality of wafers 122.sub.1 . . . 122.sub.6 having a housing 260
(see FIGS. 2A-2C) and a column of conductive elements. In the
illustrated embodiment, each column has a plurality of signal
conductors 420 (see FIG. 4A) and a plurality of ground conductors
430 (see FIG. 4A). The ground conductors may be employed within
each wafer 122.sub.1 . . . 122.sub.6 to minimize crosstalk between
signal conductors or to otherwise control the electrical properties
of the connector.
[0047] Wafers 122.sub.1 . . . 122.sub.6 may be formed by molding
housing 260 around conductive elements that form signal and ground
conductors. As with shroud 158 of backplane connector 150, housing
260 may be formed of any suitable material and may include portions
that have conductive filler or are otherwise made lossy.
[0048] In the illustrated embodiment, daughter card connector 120
is a right angle connector and has conductive elements that
traverse a right angle. As a result, opposing ends of the
conductive elements extend from perpendicular edges of the wafers
122.sub.1 . . . 122.sub.6.
[0049] Each conductive element of wafers 122.sub.1 . . . 122.sub.6
has at least one contact tail, shown collectively as contact tails
126 that can be connected to daughter card 140. Each conductive
element in daughter card connector 120 also has a mating contact
portion, shown collectively as mating contacts 124, which can be
connected to a corresponding conductive element in backplane
connector 150. Each conductive element also has an intermediate
portion between the mating contact portion and the contact tail,
which may be enclosed by or embedded within a wafer housing 260
(see FIG. 2).
[0050] The contact tails 126 electrically connect the conductive
elements within daughter card and connector 120 to conductive
elements, such as traces 142 in daughter card 140. In the
embodiment illustrated, contact tails 126 are press fit "eye of the
needle" contacts that make an electrical connection through via
holes in daughter card 140. However, any suitable attachment
mechanism may be used instead of or in addition to via holes and
press fit contact tails.
[0051] In the illustrated embodiment, each of the mating contacts
124 has a dual beam structure configured to mate to a corresponding
mating contact 154 of backplane connector 150. The conductive
elements acting as signal conductors may be grouped in pairs,
separated by ground conductors in a configuration suitable for use
as a differential electrical connector. However, embodiments are
possible for single-ended use in which the conductive elements are
evenly spaced without designated ground conductors separating
signal conductors or with a ground conductor between each signal
conductor.
[0052] In the embodiments illustrated, some conductive elements are
designated as forming a differential pair of conductors and some
conductive elements are designated as ground conductors. These
designations refer to the intended use of the conductive elements
in an interconnection system as they would be understood by one of
skill in the art. For example, though other uses of the conductive
elements may be possible, differential pairs may be identified
based on preferential coupling between the conductive elements that
make up the pair. Electrical characteristics of the pair, such as
its impedance, that make it suitable for carrying a differential
signal may provide an alternative or additional method of
identifying a differential pair. As another example, in a connector
with differential pairs, ground conductors may be identified by
their positioning relative to the differential pairs. In other
instances, ground conductors may be identified by their shape or
electrical characteristics. For example, ground conductors may be
relatively wide to provide low inductance, which is desirable for
providing a stable reference potential, but provides an impedance
that is undesirable for carrying a high speed signal.
[0053] For exemplary purposes only, daughter card connector 120 is
illustrated with six wafers 122.sub.1 . . . 122.sub.6, with each
wafer having a plurality of pairs of signal conductors and adjacent
ground conductors. As pictured, each of the wafers 122.sub.1 . . .
122.sub.6 includes one column of conductive elements. However, the
present invention is not limited in this regard, as the number of
wafers and the number of signal conductors and ground conductors in
each wafer may be varied as desired.
[0054] As shown, each wafer 122.sub.1 . . . 122.sub.6 is inserted
into front housing 130 such that mating contacts 124 are inserted
into and held within openings in front housing 130. The openings in
front housing 130 are positioned so as to allow mating contacts 154
of the backplane connector 150 to enter the openings in front
housing 130 and allow electrical connection with mating contacts
124 when daughter card connector 120 is mated to backplane
connector 150.
[0055] Daughter card connector 120 may include a support member
instead of or in addition to front housing 130 to hold wafers
122.sub.1 . . . 122.sub.6. In the pictured embodiment, stiffener
128 supports the plurality of wafers 122.sub.1 . . . 122.sub.6.
Stiffener 128 is, in the embodiment illustrated, a stamped metal
member. Though, stiffener 128 may be formed from any suitable
material. Stiffener 128 may be stamped with slots, holes, grooves
or other features that can engage a wafer.
[0056] Each wafer 122.sub.1 . . . 122.sub.6 may include attachment
features 242, 244 (see FIG. 2A-2B) that engage stiffener 128 to
locate each wafer 122 with respect to another and further to
prevent rotation of the wafer 122. Of course, the present invention
is not limited in this regard, and no stiffener need be employed.
Further, although the stiffener is shown attached to an upper and
side portion of the plurality of wafers, the present invention is
not limited in this respect, as other suitable locations may be
employed.
[0057] FIGS. 2A-2B illustrate opposing side views of an exemplary
wafer 220A. Wafer 220A may be formed in whole or in part by
injection molding of material to form housing 260 around a wafer
strip assembly such as 410A or 410B (FIG. 4). In the pictured
embodiment, wafer 220A is formed with a two shot molding operation,
allowing housing 260 to be formed of two types of material having
different material properties. Insulative portion 240 is formed in
a first shot and lossy portion 250 is formed in a second shot.
However, any suitable number and types of material may be used in
housing 260. In one embodiment, the housing 260 is formed around a
column of conductive elements by injection molding plastic.
[0058] In some embodiments, housing 260 may be provided with
openings, such as windows or slots 264.sub.1 . . . 264.sub.6, and
holes, of which hole 262 is numbered, adjacent the signal
conductors 420. These openings may serve multiple purposes,
including to: (i) ensure during an injection molding process that
the conductive elements are properly positioned, and (ii)
facilitate insertion of materials that have different electrical
properties, if so desired.
[0059] To obtain the desired performance characteristics, one
embodiment of the present invention may employ regions of different
dielectric constant selectively located adjacent signal conductors
310.sub.1B, 310.sub.2B . . . 310.sub.4B of a wafer. For example, in
the embodiment illustrated in FIGS. 2A-2C, the housing 260 includes
slots 264.sub.1 . . . 264.sub.6 in housing 260 that position air
adjacent signal conductors 310.sub.1B, 310.sub.2B . . .
310.sub.4B.
[0060] The ability to place air, or other material that has a
dielectric constant lower than the dielectric constant of material
used to form other portions of housing 260, in close proximity to
one half of a differential pair provides a mechanism to de-skew a
differential pair of signal conductors. The time it takes an
electrical signal to propagate from one end of the signal connector
to the other end is known as the propagation delay. In some
embodiments, it is desirable that each signal within a pair have
the same propagation delay, which is commonly referred to as having
zero skew within the pair. The propagation delay within a conductor
is influenced by the dielectric constant of material near the
conductor, where a lower dielectric constant means a lower
propagation delay. The dielectric constant is also sometimes
referred to as the relative permittivity. A vacuum has the lowest
possible dielectric constant with a value of 1. Air has a similarly
low dielectric constant, whereas dielectric materials, such as LCP,
have higher dielectric constants. For example, LCP has a dielectric
constant of between about 2.5 and about 4.5.
[0061] Each signal conductor of the signal pair may have a
different physical length, particularly in a right-angle connector.
According to one aspect of the invention, to equalize the
propagation delay in the signal conductors of a differential pair
even though they have physically different lengths, the relative
proportion of materials of different dielectric constants around
the conductors may be adjusted. In some embodiments, more air is
positioned in close proximity to the physically longer signal
conductor of the pair than for the shorter signal conductor of the
pair, thus lowering the effective dielectric constant around the
signal conductor and decreasing its propagation delay.
[0062] However, as the dielectric constant is lowered, the
impedance of the signal conductor rises. To maintain balanced
impedance within the pair, the size of the signal conductor in
closer proximity to the air may be increased in thickness or width.
This results in two signal conductors with different physical
geometry, but a more equal propagation delay and more inform
impedance profile along the pair.
[0063] FIG. 2C shows a wafer 220 in cross section taken along the
line 2C-2C in FIG. 2B. As shown, a plurality of differential pairs
340.sub.1 . . . 340.sub.4 are held in an array within insulative
portion 240 of housing 260. In the illustrated embodiment, the
array, in cross-section, is a linear array, forming a column of
conductive elements.
[0064] Slots 264.sub.1 . . . 264.sub.4 are intersected by the cross
section and are therefore visible in FIG. 2C. As can be seen, slots
264.sub.1 . . . 264.sub.4 create regions of air adjacent the longer
conductor in each differential pair 340.sub.1, 340.sub.2 . . .
340.sub.4. Though, air is only one example of a material with a low
dielectric constant that may be used for de-skewing a connector.
Regions comparable to those occupied by slots 264.sub.1 . . .
264.sub.4 as shown in FIG. 2C could be formed with a plastic with a
lower dielectric constant than the plastic used to form other
portions of housing 260. As another example, regions of lower
dielectric constant could be formed using different types or
amounts of fillers. For example, lower dielectric constant regions
could be molded from plastic having less glass fiber reinforcement
than in other regions.
[0065] FIG. 2C also illustrates positioning and relative dimensions
of signal and ground conductors that may be used in some
embodiments. As shown in FIG. 2C, intermediate portions of the
signal conductors 310.sub.1A . . . 310.sub.4A and 310.sub.1B . . .
310.sub.4B are embedded within housing 260 to form a column.
Intermediate portions of ground conductors 330 . . . 330.sub.4 may
also be held within housing 260 in the same column.
[0066] Ground conductors 330.sub.1, 330.sub.2 and 330.sub.3 are
positioned between two adjacent differential pairs 340.sub.1,
340.sub.2 . . . 340.sub.4 within the column. Additional ground
conductors may be included at either or both ends of the column. In
wafer 220A, as illustrated in FIG. 2C, a ground conductor 330.sub.4
is positioned at one end of the column. As shown in FIG. 2C, in
some embodiments, each ground conductor 330.sub.1 . . . 330.sub.4
is preferably wider than the signal conductors of differential
pairs 340.sub.1 . . . 340.sub.4. In the cross-section illustrated,
the intermediate portion of each ground conductor has a width that
is equal to or greater than three times the width of the
intermediate portion of a signal conductor. In the pictured
embodiment, the width of each ground conductor is sufficient to
span at least the same distance along the column as a differential
pair.
[0067] In the pictured embodiment, each ground conductor has a
width approximately five times the width of a signal conductor such
that in excess of 50% of the column width occupied by the
conductive elements is occupied by the ground conductors. In the
illustrated embodiment, approximately 70% of the column width
occupied by conductive elements is occupied by the ground
conductors 330.sub.1 . . . 330.sub.4. Increasing the percentage of
each column occupied by a ground conductor can decrease cross talk
within the connector.
[0068] Other techniques can also be used to manufacture wafer 220A
to reduce crosstalk or otherwise have desirable electrical
properties. In some embodiments, one or more portions of the
housing 260 are formed from a material that selectively alters the
electrical and/or electromagnetic properties of that portion of the
housing, thereby suppressing noise and/or crosstalk, altering the
impedance of the signal conductors or otherwise imparting desirable
electrical properties to the signal conductors of the wafer.
[0069] In the embodiment illustrated in FIGS. 2A-2C, housing 260
includes an insulative portion 240 and a lossy portion 250. In one
embodiment, the lossy portion 250 may include a thermoplastic
material filled with conducting particles. The fillers make the
portion "electrically lossy." In one embodiment, the lossy regions
of the housing are configured to reduce crosstalk between at least
two adjacent differential pairs 340.sub.1 . . . 340.sub.4. The
insulative regions of the housing may be configured so that the
lossy regions do not attenuate signals carried by the differential
pairs 340.sub.1 . . . 340.sub.4 an undesirable amount.
[0070] Materials that conduct, but with some loss, over the
frequency range of interest are referred to herein generally as
"lossy" materials. Electrically lossy materials can be formed from
lossy dielectric and/or lossy conductive materials. The frequency
range of interest depends on the operating parameters of the system
in which such a connector is used, but will generally be between
about 1 GHz and 25 GHz, though higher frequencies or lower
frequencies may be of interest in some applications. Some connector
designs may have frequency ranges of interest that span only a
portion of this range, such as 1 to 10 GHz or 3 to 15 GHz. or 3 to
6 GHz.
[0071] Electrically lossy material can be formed from material
traditionally regarded as dielectric materials, such as those that
have an electric loss tangent greater than approximately 0.003 in
the frequency range of interest. The "electric loss tangent" is the
ratio of the imaginary part to the real part of the complex
electrical permittivity of the material.
[0072] Electrically lossy materials can also be formed from
materials that are generally thought of as conductors, but are
either relatively poor conductors over the frequency range of
interest, contain particles or regions that are sufficiently
dispersed that they do not provide high conductivity or otherwise
are prepared with properties that lead to a relatively weak bulk
conductivity over the frequency range of interest. Electrically
lossy materials typically have a conductivity of about 1
siemans/meter to about 6.1.times.10.sup.7 siemans/meter, preferably
about 1 siemans/meter to about 1.times.10.sup.7 siemans/meter and
most preferably about 1 siemans/meter to about 30,000
siemans/meter.
[0073] Electrically lossy materials may be partially conductive
materials, such as those that have a surface resistivity between 1
.OMEGA./square and 10.sup.6 .OMEGA./square. In some embodiments,
the electrically lossy material has a surface resistivity between 1
.OMEGA./square and 10.sup.3 .OMEGA./square. In some embodiments,
the electrically lossy material has a surface resistivity between
10 .OMEGA./square and 100 .OMEGA./square. As a specific example,
the material may have a surface resistivity of between about 20
.OMEGA./square and 40 .OMEGA./square.
[0074] In some embodiments, electrically lossy material is formed
by adding to a binder a filler that contains conductive particles.
Examples of conductive particles that may be used as a filler to
form an electrically lossy material include carbon or graphite
formed as fibers, flakes or other particles. Metal in the form of
powder, flakes, fibers or other particles may also be used to
provide suitable electrically lossy properties. Alternatively,
combinations of fillers may be used. For example, metal plated
carbon particles may be used. Silver and nickel are suitable metal
plating for fibers. Coated particles may be used alone or in
combination with other fillers, such as carbon flake. In some
embodiments, the conductive particles disposed in the lossy portion
250 of the housing may be disposed generally evenly throughout,
rendering a conductivity of the lossy portion generally constant.
An other embodiments, a first region of the lossy portion 250 may
be more conductive than a second region of the lossy portion 250 so
that the conductivity, and therefore amount of loss within the
lossy portion 250 may vary.
[0075] The binder or matrix may be any material that will set, cure
or can otherwise be used to position the filler material. In some
embodiments, the binder may be a thermoplastic material such as is
traditionally used in the manufacture of electrical connectors to
facilitate the molding of the electrically lossy material into the
desired shapes and locations as part of the manufacture of the
electrical connector. However, many alternative forms of binder
materials may be used. Curable materials, such as epoxies, can
serve as a binder. Alternatively, materials such as thermosetting
resins or adhesives may be used. Also, while the above described
binder materials may be used to create an electrically lossy
material by forming a binder around conducting particle fillers,
the invention is not so limited. For example, conducting particles
may be impregnated into a formed matrix material or may be coated
onto a formed matrix material, such as by applying a conductive
coating to a plastic housing. As used herein, the term "binder"
encompasses a material that encapsulates the filler, is impregnated
with the filler or otherwise serves as a substrate to hold the
filler.
[0076] Preferably, the fillers will be present in a sufficient
volume percentage to allow conducting paths to be created from
particle to particle. For example, when metal fiber is used, the
fiber may be present in about 3% to 40% by volume. The amount of
filler may impact the conducting properties of the material.
[0077] Filled materials may be purchased commercially, such as
materials sold under the trade name Celestran.RTM. by Ticona. A
lossy material, such as lossy conductive carbon filled adhesive
preform, such as those sold by Techfilm of Billerica, Mass., US may
also be used. This preform can include an epoxy binder filled with
carbon particles. The binder surrounds carbon particles, which acts
as a reinforcement for the preform. Such a preform may be inserted
in a wafer 220A to form all or part of the housing and may be
positioned to adhere to ground conductors in the wafer. In some
embodiments, the preform may adhere through the adhesive in the
preform, which may be cured in a heat treating process. Various
forms of reinforcing fiber, in woven or non-woven form, coated or
non-coated may be used. Non-woven carbon fiber is one suitable
material. Other suitable materials, such as custom blends as sold
by RTP Company, can be employed, as the present invention is not
limited in this respect.
[0078] In the embodiment illustrated in FIG. 2C, the wafer housing
260 is molded with two types of material. In the pictured
embodiment, lossy portion 250 is formed of a material having a
conductive filler, whereas the insulative portion 240 is formed
from an insulative material having little or no conductive fillers,
though insulative portions may have fillers, such as glass fiber,
that alter mechanical properties of the binder material or impacts
other electrical properties, such as dielectric constant, of the
binder. In one embodiment, the insulative portion 240 is formed of
molded plastic and the lossy portion is formed of molded plastic
with conductive fillers. In some embodiments, the lossy portion 250
is sufficiently lossy that it attenuates radiation between
differential pairs to a sufficient amount that crosstalk is reduced
to a level that a separate metal plate is not required.
[0079] To prevent signal conductors 310.sub.1A, 310.sub.1B . . .
310.sub.4A, and 310.sub.4B from being shorted together and/or from
being shorted to ground by lossy portion 250, insulative portion
240, formed of a suitable dielectric material, may be used to
insulate the signal conductors. The insulative materials may be,
for example, a thermoplastic binder into which non-conducting
fibers are introduced for added strength, dimensional stability and
to reduce the amount of higher priced binder used. Glass fibers, as
in a conventional electrical connector, may have a loading of about
30% by volume. It should be appreciated that in other embodiments,
other materials may be used, as the invention is not so
limited.
[0080] In the embodiment of FIG. 2C, the lossy portion 250 includes
a parallel region 336 and perpendicular regions 334.sub.1 . . .
334.sub.4. In one embodiment, perpendicular regions 334.sub.1 . . .
334.sub.4 are disposed between adjacent conductive elements that
form separate differential pairs 340.sub.1 . . . 340.sub.4.
[0081] In some embodiments, the lossy regions 336 and 334.sub.1 . .
. 334.sub.4 of the housing 260 and the ground conductors 330.sub.1
. . . 330.sub.4 cooperate to shield the differential pairs
340.sub.1 . . . 340.sub.4 to reduce crosstalk. The lossy regions
336 and 334.sub.1 . . . 334.sub.4 may be grounded by being
electrically connected to one or more ground conductors. This
configuration of lossy material in combination with ground
conductors 330.sub.1 . . . 330.sub.4 reduces crosstalk between
differential pairs within a column.
[0082] As shown in FIG. 2C, portions of the ground conductors
330.sub.1 . . . 330.sub.4, may be electrically connected to regions
336 and 334.sub.1 . . . 334.sub.4 by molding portion 250 around
ground conductors 340.sub.1 . . . 340.sub.4. In some embodiments,
ground conductors may include openings through which the material
forming the housing can flow during molding. For example, the cross
section illustrated in FIG. 2C is taken through an opening 332 in
ground conductor 330.sub.1. Though not visible in the cross section
of FIG. 2C, other openings in other ground conductors such as
330.sub.2 . . . 330.sub.4 may be included.
[0083] Material that flows through openings in the ground
conductors allows perpendicular portions 334.sub.1 . . . 334.sub.4
to extend through ground conductors even though a mold cavity used
to form a wafer 220A has inlets on only one side of the ground
conductors. Additionally, flowing material through openings in
ground conductors as part of a molding operation may aid in
securing the ground conductors in housing 260 and may enhance the
electrical connection between the lossy portion 250 and the ground
conductors. However, other suitable methods of forming
perpendicular portions 334.sub.1 . . . 334.sub.4 may also be used,
including molding wafer 320A in a cavity that has inlets on two
sides of ground conductors 330.sub.1 . . . 330.sub.4. Likewise,
other suitable methods for securing the ground contacts 330 may be
employed, as the present invention is not limited in this
respect.
[0084] Forming the lossy portion 250 of the housing from a moldable
material can provide additional benefits. For example, the lossy
material at one or more locations can be configured to set the
performance of the connector at that location. For example,
changing the thickness of a lossy portion to space signal
conductors closer to or further away from the lossy portion 250 can
alter the performance of the connector. As such, electromagnetic
coupling between one differential pair and ground and another
differential pair and ground can be altered, thereby configuring
the amount of loss for radiation between adjacent differential
pairs and the amount of loss to signals carried by those
differential pairs. As a result, a connector according to
embodiments of the invention may be capable of use at higher
frequencies than conventional connectors, such as for example at
frequencies between 10-15 GHz.
[0085] As shown in the embodiment of FIG. 2C, wafer 220A is
designed to carry differential signals. Thus, each signal is
carried by a pair of signal conductors 310A and 310.sub.1B, . . .
310.sub.4A and 310.sub.4B. Preferably, each signal conductor is
closer to the other conductor in its pair than it is to a conductor
in an adjacent pair. For example, a pair 340.sub.1 carries one
differential signal, and pair 340.sub.2 carries another
differential signal. As can be seen in the cross section of FIG.
2C, signal conductor 310.sub.1B is closer to signal conductor
310.sub.1A than to signal conductor 310.sub.2A. Perpendicular lossy
regions 334.sub.1 . . . 334.sub.4 may be positioned between pairs
to provide shielding between the adjacent differential pairs in the
same column.
[0086] Lossy material may also be positioned to reduce the
crosstalk between adjacent pairs in different columns. FIG. 3
illustrates a cross-sectional view similar to FIG. 2C but with a
plurality of subassemblies or wafers 320A, 320B aligned side to
side to form multiple parallel columns.
[0087] As illustrated in FIG. 3, the plurality of signal conductors
340 may be arranged in differential pairs in a plurality of columns
formed by positioning wafers side by side. It is not necessary that
each wafer be the same and different types of wafers may be
used.
[0088] It may be desirable for all types of wafers used to
construct a daughter card connector to have an outer envelope of
approximately the same dimensions so that all wafers fit within the
same enclosure or can be attached to the same support member, such
as stiffener 128 (FIG. 1). However, by providing different
placement of the signal conductors, ground conductors and lossy
portions in different wafers, the amount that the lossy material
reduces crosstalk relative for the amount that it attenuates
signals may be more readily configured. In one embodiment, two
types of wafers are used, which are illustrated in FIG. 3 as
subassemblies or wafers 320A and 320B.
[0089] Each of the wafers 320B may include structures similar to
those in wafer 320A as illustrated in FIGS. 2A, 2B and 2C. As shown
in FIG. 3, wafers 320B include multiple differential pairs, such as
pairs 340.sub.5, 340.sub.6, 340.sub.7 and 340.sub.8. The signal
pairs may be held within an insulative portion, such as 240B of a
housing. Slots or other structures (not numbered) may be formed
within the housing for skew equalization in the same way that slots
264.sub.1 . . . 264.sub.6 are formed in a wafer 220A.
[0090] The housing for a wafer 320B may also include lossy
portions, such as lossy portions 250B. As with lossy portions 250
described in connection with wafer 320A in FIG. 2C, lossy portions
250B may be positioned to reduce crosstalk between adjacent
differential pairs. The lossy portions 250B may be shaped to
provide a desirable level of crosstalk suppression without causing
an undesired amount of signal attenuation.
[0091] In the embodiment illustrated, lossy portion 250B may have a
substantially parallel region 336B that is parallel to the columns
of differential pairs 3405 . . . 3408. Each lossy portion 250B may
further include a plurality of perpendicular regions 3341B . . .
3345B, which extend from the parallel region 336B. The
perpendicular regions 3341B . . . 3345B may be spaced apart and
disposed between adjacent differential pairs within a column.
[0092] Wafers 320B also include ground conductors, such as ground
conductors 330.sub.5 . . . 330.sub.9. As with wafers 320A, the
ground conductors are positioned adjacent differential pairs
340.sub.5 . . . 340.sub.8. Also, as in wafers 320A, the ground
conductors generally have a width greater than the width of the
signal conductors. In the embodiment pictured in FIG. 3, ground
conductors 330.sub.5 . . . 330.sub.8 have generally the same shape
as ground conductors 330.sub.1 . . . 330.sub.4 in a wafer 320A.
However, in the embodiment illustrated, ground conductor 330.sub.9
has a width that is less than the ground conductors 330.sub.5 . . .
330.sub.8 in wafer 320B.
[0093] Ground conductor 330.sub.9 is narrower to provide desired
electrical properties without requiring the wafer 320B to be
undesirably wide. Ground conductor 330.sub.9 has an edge facing
differential pair 340.sub.8. Accordingly, differential pair
340.sub.8 is positioned relative to a ground conductor similarly to
adjacent differential pairs, such as differential pair 330.sub.8 in
wafer 320B or pair 340.sub.4 in a wafer 320A. As a result, the
electrical properties of differential pair 340.sub.8 are similar to
those of other differential pairs. By making ground conductor
330.sub.9 narrower than ground conductors 330.sub.8 or 330.sub.4,
wafer 320B may be made with a smaller size.
[0094] A similar small ground conductor could be included in wafer
320A adjacent pair 340.sub.1. However, in the embodiment
illustrated, pair 340.sub.1 is the shortest of all differential
pairs within daughter card connector 120. Though including a narrow
ground conductor in wafer 320A could make the ground configuration
of differential pair 340.sub.1 more similar to the configuration of
adjacent differential pairs in wafers 320A and 320B, the net effect
of differences in ground configuration may be proportional to the
length of the conductor over which those differences exist. Because
differential pair 340.sub.1 is relatively short, in the embodiment
of FIG. 3, a second ground conductor adjacent to differential pair
340.sub.1, though it would change the electrical characteristics of
that pair, may have relatively little net effect. However, in other
embodiments, a further ground conductor may be included in wafers
320A.
[0095] FIG. 3 illustrates a further feature possible when using
multiple types of wafers to form a daughter card connector. Because
the columns of contacts in wafers 320A and 320B have different
configurations, when wafer 320A is placed side by side with wafer
320B, the differential pairs in wafer 320A are more closely aligned
with ground conductors in wafer 320B than with adjacent pairs of
signal conductors in wafer 320B. Conversely, the differential pairs
of wafer 320B are more closely aligned with ground conductors than
adjacent differential pairs in the wafer 320A.
[0096] For example, differential pair 340.sub.6 is proximate ground
conductor 330.sub.2 in wafer 320A. Similarly, differential pair
340.sub.3 in wafer 320A is proximate ground conductor 330.sub.7 in
wafer 320B. In this way, radiation from a differential pair in one
column couples more strongly to a ground conductor in an adjacent
column than to a signal conductor in that column. This
configuration reduces crosstalk between differential pairs in
adjacent columns.
[0097] Wafers with different configurations may be formed in any
suitable way. FIG. 4A illustrates a step in the manufacture of
wafers 320A and 320B according to one embodiment. In the
illustrated embodiment, wafer strip assemblies, each containing
conductive elements in a configuration desired for one column of a
daughter card connector, are formed. A housing is then molded
around the conductive elements in each wafer strip assembly in an
insert molding operation to form a wafer.
[0098] To facilitate the manufacture of wafers, signal conductors,
of which signal conductor 420 is numbered, and ground conductors,
of which ground conductor 430 is numbered, may be held together on
a lead frame 400 as shown in FIG. 4A. As shown, the signal
conductors 420 and the ground conductors 430 are attached to one or
more carrier strips 402. In one embodiment, the signal conductors
and ground conductors are stamped for many wafers on a single
sheet. The sheet may be metal or may be any other material that is
conductive and provides suitable mechanical properties for making a
conductive element in an electrical connector. Phosphor-bronze,
beryllium copper and other copper alloys are example of materials
that may be used.
[0099] FIG. 4A illustrates a portion of a sheet of metal in which
wafer strip assemblies 410A, 410B have been stamped. Wafer strip
assemblies 410A, 410B may be used to form wafers 320A and 320B,
respectively. Conductive elements may be retained in a desired
position on carrier strips 402. The conductive elements may then be
more readily handled during manufacture of wafers. Once material is
molded around the conductive elements, the carrier strips may be
severed to separate the conductive elements. The wafers may then be
assembled into daughter board connectors of any suitable size.
[0100] FIG. 4A also provides a more detailed view of features of
the conductive elements of the daughter card wafers. The width of a
ground conductor, such as ground conductor 430, relative to a
signal conductor, such as signal conductor 420, is apparent. Also,
openings in ground conductors, such as opening 332, are
visible.
[0101] The wafer strip assemblies shown in FIG. 4A provide just one
example of a component that may be used in the manufacture of
wafers. For example, in the embodiment illustrated in FIG. 4A, the
lead frame 400 includes tie bars 452, 454 and 456 that connect
various portions of the signal conductors 420 and/or ground strips
430 to the lead frame 400. These tie bars may be severed during
subsequent manufacturing processes to provide electronically
separate conductive elements. A sheet of metal may be stamped such
that one or more additional carrier strips are formed at other
locations and/or bridging members between conductive elements may
be employed for positioning and support of the conductive elements
during manufacture. Accordingly, the details shown in FIG. 4A are
illustrative and not a limitation on the invention.
[0102] Although the lead frame 400 is shown as including both
ground conductors 430 and the signal conductors 420, the present
invention is not limited in this respect. For example, the
respective conductors may be formed in two separate lead frames.
Indeed, no lead frame need be used and individual conductive
elements may be employed during manufacture. It should be
appreciated that molding over one or both lead frames or the
individual conductive elements need not be performed at all, as the
wafer may be assembled by inserting ground conductors and signal
conductors into preformed housing portions, which may then be
secured together with various features including snap fit
features.
[0103] FIG. 4B illustrates a detailed view of the mating contact
end of a differential pair 424.sub.1 positioned between two ground
mating contacts 434.sub.1 and 434.sub.2. As illustrated, the ground
conductors may include mating contacts of different sizes. The
embodiment pictured has a large mating contact 434.sub.2 and a
small mating contact 434.sub.1. To reduce the size of each wafer,
small mating contacts 434.sub.1 may be positioned on one or both
ends of the water.
[0104] FIG. 4B illustrates features of the mating contact portions
of the conductive elements within the wafers forming daughter board
connector 120. FIG. 4B illustrates a portion of the mating contacts
of a wafer configured as wafer 320B. The portion shown illustrates
a mating contact 434.sub.1 such as may be used at the end of a
ground conductor 330.sub.9 (FIG. 3). Mating contacts 424.sub.1 may
form the mating contact portions of signal conductors, such as
those in differential pair 340.sub.8 (FIG. 3). Likewise, mating
contact 434.sub.2 may form the mating contact portion of a ground
conductor, such as ground conductor 330.sub.8 (FIG. 3).
[0105] In the embodiment illustrated in FIG. 4B, each of the mating
contacts on a conductive element in a daughter card wafer is a dual
beam contact. Mating contact 434.sub.1 includes beams 460.sub.1 and
460.sub.2. Mating contacts 424.sub.1 includes four beams, two for
each of the signal conductors of the differential pair terminated
by mating contact 424.sub.1. In the illustration of FIG. 4B, beams
460.sub.3 and 460.sub.4 provide two beams for a contact for one
signal conductor of the pair and beams 460.sub.5 and 460.sub.6
provide two beams for a contact for a second signal conductor of
the pair. Likewise, mating contact 434.sub.2 includes two beams
460.sub.7 and 460.sub.8.
[0106] Each of the beams includes a mating surface, of which mating
surface 462 on beam 460.sub.1 is numbered. To form a reliable
electrical connection between a conductive element in the daughter
card connector 120 and a corresponding conductive element in
backplane connector 150, each of the beams 460.sub.1 . . .
460.sub.8 may be shaped to press against a corresponding mating
contact in the backplane connector 150 with sufficient mechanical
force to create a reliable electrical connection. Having two beams
per contact increases the likelihood that an electrical connection
will be formed even if one beam is damaged, contaminated or
otherwise precluded from making an effective connection.
[0107] Each of beams 460.sub.1 . . . 460.sub.8 has a shape that
generates mechanical force for making an electrical connection to a
corresponding contact. In the embodiment of FIG. 4B, the signal
conductors terminating at mating contact 424.sub.1 may have
relatively narrow intermediate portions 484.sub.1 and 484.sub.2
within the housing of wafer 320D. However, to form an effective
electrical connection, the mating contact portions 424.sub.1 for
the signal conductors may be wider than the intermediate portions
484.sub.1 and 484.sub.2. Accordingly, FIG. 4B shows broadening
portions 480.sub.1 and 480.sub.2 associated with each of the signal
conductors.
[0108] In the illustrated embodiment, the ground conductors
adjacent broadening portions 480.sub.1 and 480.sub.2 are shaped to
conform to the adjacent edge of the signal conductors. Accordingly,
mating contact 434.sub.1 for a ground conductor has a complementary
portion 482.sub.1 with a shape that conforms to broadening portion
480.sub.1. Likewise, mating contact 434.sub.2 has a complementary
portion 482.sub.2 that conforms to broadening portion 480.sub.2. By
incorporating complementary portions in the ground conductors, the
edge-to-edge spacing between the signal conductors and adjacent
ground conductors remains relatively constant, even as the width of
the signal conductors change at the mating contact region to
provide desired mechanical properties to the beams. Maintaining a
uniform spacing may further contribute to desirable electrical
properties for an interconnection system according to an embodiment
of the invention.
[0109] Some or all of the construction techniques employed within
daughter card connector 120 for providing desirable characteristics
may be employed in backplane connector 150. In the illustrated
embodiment, backplane connector 150, like daughter card connector
120, includes features for providing desirable signal transmission
properties. Signal conductors in backplane connector 150 are
arranged in columns, each containing differential pairs
interspersed with ground conductors. The ground conductors are wide
relative to the signal conductors. Also, adjacent columns have
different configurations. Some of the columns may have narrow
ground conductors at the end to save space while providing a
desired ground configuration around signal conductors at the ends
of the columns. Additionally, ground conductors in one column may
be positioned adjacent to differential pairs in an adjacent column
as a way to reduce crosstalk from one column to the next. Further,
lossy material may be selectively placed within the shroud of
backplane connector 150 to reduce crosstalk, without providing an
undesirable level attenuation for signals. Further, adjacent
signals and grounds may have conforming portions so that in
locations where the profile of either a signal conductor or a
ground conductor changes, the signal-to-ground spacing may be
maintained.
[0110] FIGS. 5A-5B illustrate an embodiment of a backplane
connector 150 in greater detail. In the illustrated embodiment,
backplane connector 150 includes a shroud 510 with walls 512 and
floor 514. Conductive elements are inserted into shroud 510. In the
embodiment shown, each conductive element has a portion extending
above floor 514. These portions form the mating contact portions of
the conductive elements, collectively numbered 154. Each conductive
element has a portion extending below floor 514. These portions
form the contact tails and are collectively numbered 156.
[0111] The conductive elements of backplane connector 150 are
positioned to align with the conductive elements in daughter card
connector 120. Accordingly, FIG. 5A shows conductive elements in
backplane connector 150 arranged in multiple parallel columns. In
the embodiment illustrated, each of the parallel columns includes
multiple differential pairs of signal conductors, of which
differential pairs 540.sub.1, 540.sub.2 . . . 540.sub.4 are
numbered. Each column also includes multiple ground conductors. In
the embodiment illustrated in FIG. 5A, ground conductors 530.sub.1,
530.sub.2 . . . 530.sub.5 are numbered.
[0112] Ground conductors 530.sub.1 . . . 530.sub.5 and differential
pairs 540.sub.1 . . . 540.sub.4 are positioned to form one column
of conductive elements within backplane connector 150. That column
has conductive elements positioned to align with a column of
conductive elements as in a wafer 320B (FIG. 3). An adjacent column
of conductive elements within backplane connector 150 may have
conductive elements positioned to align with mating contact
portions of a wafer 320A. The columns in backplane connector 150
may alternate configurations from column to column to match the
alternating pattern of wafers 320A, 320B shown in FIG. 3.
[0113] Ground conductors 530.sub.2, 530.sub.3 and 530.sub.4 are
shown to be wide relative to the signal conductors that make up the
differential pairs by 540.sub.1 . . . 540.sub.4. Narrower ground
conductive elements, which are narrower relative to ground
conductors 530.sub.2, 530.sub.3 and 530.sub.4, are included at each
end of the column. In the embodiment illustrated in FIG. 5A,
narrower ground conductors 530.sub.1 and 530.sub.5 are including at
the ends of the column containing differential pairs 540.sub.1 . .
. 540.sub.4 and may, for example, mate with a ground conductor from
daughter card 120 with a mating contact portion shaped as mating
contact 434.sub.1 (FIG. 4B).
[0114] FIG. 5B shows a view of backplane connector 150 taken along
the line labeled B-B in FIG. 5A. In the illustration of FIG. 5B, an
alternating pattern of columns of 560A-560B is visible. A column
containing differential pairs 540.sub.1 . . . 540.sub.4 is shown as
column 560B.
[0115] FIG. 5B shows that shroud 510 may contain both insulative
and lossy regions. In the illustrated embodiment, each of the
conductive elements of a differential pair, such as differential
pairs 540.sub.1 . . . 540.sub.4, is held within an insulative
region 522. Lossy regions 520 may be positioned between adjacent
differential pairs within the same column and between adjacent
differential pairs in adjacent columns. Lossy regions 520 may
connect to the ground contacts such as 530.sub.1 . . . 530.sub.5.
Sidewalls 512 may be made of either insulative or lossy
material.
[0116] FIGS. 6A, 6B and 6C illustrate in greater detail conductive
elements that may be used in forming backplane connector 150. FIG.
6A shows multiple wide ground contacts 530.sub.2, 530.sub.3 and
530.sub.4. In the configuration shown in FIG. 6A, the ground
contacts are attached to a carrier strip 620. The ground contacts
may be stamped from a long sheet of metal or other conductive
material, including a carrier strip 620. The individual contacts
may be severed from carrier strip 620 at any suitable time during
the manufacturing operation.
[0117] As can be seen, each of the ground contacts has a mating
contact portion shaped as a blade. For additional stiffness, one or
more stiffening structures may be formed in each contact. In the
embodiment of FIG. 6A, a rib, such as 610 is formed in each of the
wide ground conductors.
[0118] Each of the wide ground conductors, such as 530.sub.2 . . .
530.sub.4 includes two contact tails. For ground conductor
530.sub.2 contact tails 656.sub.1 and 656.sub.2 are numbered.
Providing two contact tails per wide ground conductor provides for
a more even distribution of grounding structures throughout the
entire interconnection system, including within backplane 160
because each of contact tails 656.sub.1 and 656.sub.2 will engage a
ground via within backplane 160 that will be parallel and adjacent
a via carrying a signal. FIG. 4A illustrates that two ground
contact tails may also be used for each ground conductor in
daughter card connector.
[0119] FIG. 6B shows a stamping containing narrower ground
conductors, such as ground conductors 530.sub.1 and 530.sub.5. As
with the wider ground conductors shown in FIG. 6A, the narrower
ground conductors of FIG. 6B have a mating contact portion shaped
like a blade.
[0120] As with the stamping of FIG. 6A, the stamping of FIG. 6B
containing narrower grounds includes a carrier strip 630 to
facilitate handling of the conductive elements. The individual
ground conductors may be severed from carrier strip 630 at any
suitable time, either before or after insertion into backplane
connector shroud 510.
[0121] In the embodiment illustrated, each of the narrower ground
conductors, such as 530.sub.1 and 530.sub.2, contains a single
contact tail such as 656.sub.3 on ground conductor 530.sub.1 or
contact tail 656.sub.4 on ground conductor 530.sub.5. Even though
only one ground contact tail is included, the relationship between
number of signal contacts is maintained because narrow ground
conductors as shown in FIG. 6B are used at the ends of columns
where they are adjacent a single signal conductor. As can be seen
from the illustration in FIG. 6B, each of the contact tails for a
narrower ground conductor is offset from the center line of the
mating contact in the same way that contact tails 656.sub.1 and
656.sub.2 are displaced from the center line of wide contacts. This
configuration may be used to preserve the spacing between a ground
contact tail and an adjacent signal contact tail.
[0122] As can be seen in FIG. 5A, in the pictured embodiment of
backplane connector 150, the narrower ground conductors, such as
530.sub.1 and 530.sub.5, are also shorter than the wider ground
conductors such as 530.sub.2 . . . 530.sub.4. The narrower ground
conductors shown in FIG. 6B do not include a stiffening structure,
such as ribs 610 (FIG. 6A). However, embodiments of narrower ground
conductors may be formed with stiffening structures.
[0123] FIG. 6C shows signal conductors that may be used to form
backplane connector 150. The signal conductors in FIG. 6C, like the
ground conductors of FIGS. 6A and 6B, may be stamped from a sheet
of metal. In the embodiment of FIG. 6C, the signal conductors are
stamped in pairs, such as pairs 540.sub.1 and 540.sub.2. The
stamping of FIG. 6C includes a carrier strip 640 to facilitate
handling of the conductive elements. The pairs, such as 540.sub.1
and 540.sub.2, may be severed from carrier strip 640 at any
suitable point during manufacture.
[0124] As can be seen from FIGS. 5A, 6A, 6B and 6C, the signal
conductors and ground conductors for backplane connector 150 may be
shaped to conform to each other to maintain a consistent spacing
between the signal conductors and ground conductors. For example,
ground conductors have projections, such as projection 660, that
position the ground conductor relative to floor 514 of shroud 510.
The signal conductors have complementary portions, such as
complementary portion 662 (FIG. 6C) so that when a signal conductor
is inserted into shroud 510 next to a ground conductor, the spacing
between the edges of the signal conductor and the ground conductor
stays relatively uniform, even in the vicinity of projections
660.
[0125] Likewise, signal conductors have projections, such as
projections 664 (FIG. 6C). Projection 664 may act as a retention
feature that holds the signal conductor within the floor 514 of
backplane connector shroud 510 (FIG. 5A). Ground conductors may
have complementary portions, such as complementary portion 666
(FIG. 6A). When a signal conductor is placed adjacent a ground
conductor, complementary portion 666 maintains a relatively uniform
spacing between the edges of the signal conductor and the ground
conductor, even in the vicinity of projection 664.
[0126] FIGS. 6A, 6B and 6C illustrate examples of projections in
the edges of signal and ground conductors and corresponding
complementary portions formed in an adjacent signal or ground
conductor. Other types of projections may be formed and other
shapes of complementary portions may likewise be formed.
[0127] To facilitate use of signal and ground conductors with
complementary portions, backplane connector 150 may be manufactured
by inserting signal conductors and ground conductors into shroud
510 from opposite sides. As can be seen in FIG. 5A, projections
such as 660 (FIG. 6A) of ground conductors press against the bottom
surface of floor 514. Backplane connector 150 may be assembled by
inserting the ground conductors into shroud 510 from the bottom
until projections 660 engage the underside of floor 514. Because
signal conductors in backplane connector 150 are generally
complementary to the ground conductors, the signal conductors have
narrow portions adjacent the lower surface of floor 514. The wider
portions of the signal conductors are adjacent the top surface of
floor 514. Because manufacture of a backplane connector may be
simplified if the conductive elements are inserted into shroud 510
narrow end first, backplane connector 150 may be assembled by
inserting signal conductors into shroud 510 from the upper surface
of floor 514. The signal conductors may be inserted until
projections, such as projection 664, engage the upper surface of
the floor. Two-sided insertion of conductive elements into shroud
510 facilitates manufacture of connector portions with conforming
signal and ground conductors.
[0128] FIGS. 7A and 7B illustrate additional detail of construction
techniques that may be used to improve the electrical properties of
a connector. As described above, lossy material may be selectively
positioned near signal conductors to reduce crosstalk without
causing an undesirably large attenuation of signals carried by the
signal conductors. FIG. 7A illustrates that regions of lossy
material may be set back from the edges of the ground conductors
that are adjacent signal conductors as a way to reduce attenuation
of signals. Taking ground conductor 330.sub.8 as illustrative,
ground conductor 330.sub.8 has an edge 720 facing signal conductor
740.sub.1 of pair 340.sub.8. Lossy region 734 is set back from the
edge 720 by a distance D.
[0129] In one embodiment, the width of the setback D is between
approximately 0.1 mm and about 1 mm. In some embodiments, the
setback may be as large as possible, though not so large as to make
lossy region 734 so narrow that it cannot be effectively formed.
However, it should be appreciated that in other embodiments, the
setback D may be different and may depend on the width of ground
conductors, such as ground conductor 330.sub.8. Accordingly, the
present invention is not limited in this respect. By including such
a setback, attenuation of the common mode component of the signal
carried by differential pair 340.sub.4 is reduced in comparison to
embodiments in which lossy region 734 extends to or beyond edge
720. Nonetheless, lossy region 734 is positioned to attenuate
radiation emanating from pair 340.sub.8 that could cause crosstalk
on adjacent signal conductors or radiation propagating toward pair
340.sub.8 that could cause crosstalk on differential pair
340.sub.8.
[0130] The space created by having a setback of the lossy region
734 from the edge 720 may be occupied with insulative material,
such as an insulative segment 724 of the insulative portion 240 of
the wafer housing. Alternatively, the setback portion may be
occupied by air or any other suitable material that is less lossy
than lossy region 734.
[0131] FIG. 7B provides an idealized representation of desirable
locations for lossy material within a connector according to an
embodiment of the invention. FIG. 7B illustrates two adjacent
columns of conductive elements within a connector. In FIG. 7B,
columns 710A and 710B are shown. As pictured in FIG. 7A, each
column includes ground conductors, of which ground conductors
330.sub.3, 330.sub.4, 330.sub.7, 330.sub.8 and 330.sub.9 are
numbered. Also, the columns include differential pairs, of which
differential pairs 340.sub.3, 340.sub.4, 340.sub.7 and 340.sub.8
are numbered. FIG. 7B illustrates desirable placement locations for
lossy regions, of which lossy regions 700.sub.1 and 700.sub.2 are
numbered.
[0132] In the embodiment illustrated, the lossy regions occupy the
volume between ground conductors in adjacent columns. The lossy
regions are generally centered between adjacent differential pairs
in the two columns. For example, lossy region 700.sub.1 occupies
the volume between ground conductor 330.sub.4 in column 710A and
ground conductor 330.sub.8 in column 710B. Lossy region 700.sub.1
is centered between differential pair 340.sub.4 in column 710A and
340.sub.8 in column 710B. Likewise, lossy region 700.sub.2 spans
the volume between ground conductor 330.sub.3 and 330.sub.8 and is
centered around the center line between differential pair 340.sub.4
and 340.sub.7.
[0133] With this placement of lossy material, crosstalk between
adjacent differential pairs, whether in the same column or an
adjacent column, may be reduced by the lossy material and shielding
effects of the ground conductors. However, the regions proximate
the signal conductors are free of lossy material, thereby limiting
the amount of attenuation of signals carried by the differential
pairs.
[0134] In comparing the representation of FIG. 7B with the
implementation according to the embodiment pictured in FIG. 7A, it
can be seen that the lossy regions depicted in the embodiment of
FIG. 7A generally occupy the locations indicated by lossy regions
such as 700.sub.1 and 700.sub.2 in FIG. 7B. The configuration of
FIG. 7A differs from the idealized representation of FIG. 7B so
that the configuration of FIG. 7A is readily molded. To facilitate
molding, the lossy regions extend generally perpendicular to the
major surfaces of wafers 320A and 320B. Further, all lossy regions
extend from one surface of each wafer, shown as the upper surface
in FIG. 7B. Lossy regions comparable to the lossy regions depicted
in FIG. 7B that are angled with respect to the normal surface of
the wafers are formed with a combination of sub-regions of lossy
material comprising sub-regions that extend along the upper surface
of one of the wafers and extend perpendicular to the surfaces. For
example, region 700, in the idealized representation may be molded
using sub-regions 750, 750.sub.2 and 750.sub.5 (FIG. 7A). However,
modifications to the construction of wafers, such as 320A and 320B,
may be made to more nearly resemble the configuration illustrated
in FIG. 7B. FIG. 8 illustrates an example of one such
variation.
[0135] As shown in FIG. 8, structures are incorporated into the
wafers, such as wafers 820A and 820B to expand the shielding
effects in the volume between ground conductors in adjacent
columns. Because each column is implemented in a separate wafer,
there is no continuous structure that occupies the entire volume
between ground conductors in adjacent columns. By incorporating
structures that electrically connect the lossy region in one wafer
to the lossy region in an adjacent wafer, the resulting structure
may more nearly resemble the configuration of FIG. 7B in which
continuous regions, such as region 700.sub.1 and 700.sub.2, span
the volume between ground conductors in adjacent columns and are
electrically connected to the ground conductors in adjacent
columns. In the embodiment of FIG. 8, an electrical connection is
formed between lossy regions in adjacent wafers by incorporating
spring fingers, such as spring finger 830. Spring fingers may be
formed as projections from ground conductors within one or both of
the wafers or may be formed in any other suitable way.
[0136] Alternative embodiments in which the positioning of lossy
material is configured to reduce crosstalk without producing an
unacceptably large attenuation of signals are illustrated in
connection with FIGS. 9A, 9B and 9C. In these embodiments, the
lossy material is segmented into separate regions that are
interspersed with regions of insulative material. The regions of
lossy material may be positioned adjacent signal conductors to
reduce crosstalk between adjacent signal conductors. By positioning
lossy material in selected regions, the attenuation and signals
carried by the signal conductors may be reduced. By appropriate
selection of the configuration of the regions of lossy material,
the lossy material may exhibit a suitable combination of effects on
the performance of the connector.
[0137] FIGS. 9A-9C illustrate cross-sectional representations of
lossy material that may be incorporated in a wafer according to
alternative embodiments of the present invention. Lossy material
configured as illustrated may be incorporated into any of the
above-described electrical connector components. Regions of lossy
material may be separated by openings or voids in portions of the
lossy material. The openings may be formed in any suitable way.
[0138] FIGS. 9A-9C illustrate various configurations of lossy
material with such openings. The openings may be in one or both of
the parallel region and the perpendicular region of the lossy
material. An opening may be configured as a hole, gap, notch, or
other volume free of lossy material of other suitable shape, as the
invention is not limited in this respect. The openings in the lossy
regions may contain air. However, as illustrated in FIGS. 2A and
2C, the lossy material 250 and insulative material 240 are molded
together to define housing 260 of a wafer. Accordingly, openings in
lossy material may be filled with insulative material 240. Such
openings may be formed by first molding the lossy material in the
desired segments and then over-molding with insulative material
that fills the openings. Alternatively, the openings may be formed
by molding the insulative material with portions occupying the
volumes in which the openings are to be formed. When over-molding
lossy material on such insulative material, the lossy material will
be formed with openings in the desired locations.
[0139] FIG. 9A illustrates lossy material in a wafer, such as wafer
320A or 320B. The portion illustrated is in the vicinity of an
intermediate portion of a differential pair along a fraction of its
length. Portions with similar construction may be positioned along
the entire length of the intermediate portion of the differential
pair and along other differential pairs. In the embodiment of FIG.
9A, the opening is in the form of a gap 938 that separates the
lossy material into segments 910.sub.1 and 910.sub.2.
[0140] Each segment 910.sub.1 and 910.sub.2 may include a parallel
region 936A, 936B and one or more perpendicular regions, such as
perpendicular regions 934.sub.1 . . . 934.sub.4. A plurality of
channels, of which channel 932 is illustrated, may be formed having
a bottom defined by the parallel region 936A, 936B and sides
defined by adjacent perpendicular regions 934.sub.1 . . .
934.sub.4. Each channel 932 may be configured to receive a
differential pair so that unwanted radiation emanating from the
differential pair or radiating toward the differential pair is
attenuated in the lossy material.
[0141] Each of the plurality of segments 910.sub.1 or 910.sub.2 may
include at least a portion of at least one of the plurality of
channels 932 separated by an opening or gap, such as gap 938, in
the lossy material. As shown, perpendicular regions 934.sub.1 . . .
934.sub.2 of a plurality of segments 910.sub.1 and 910.sub.2 may be
aligned with each other such that channel 932 spans the plurality
of segments, such as segments 910.sub.1 and 910.sub.2 of lossy
material. When formed in a wafer such as 320A or 320B, channel 932
and gap 938 may be occupied by less lossy material used to form the
housing of the wafer. However, any suitable technique may be used
to form a gap and a channel.
[0142] FIG. 9A illustrates two segments. However, the number of
segments formed may depend on one or more factors influencing the
design of an overall connector. For example, more segments may be
formed along the length of a longer differential pair than along
the length of a shorter differential pair. The number of segments
may also depend on the number of regions along the length of a
differential pair where crosstalk suppression is desired or where
avoidance of signal attenuation is desired. For example, segments
of lossy material may be placed in a region where one differential
pair is routed close to a second differential pair. Conversely, a
gap in the lossy material, forming separate segments, may be
desired proximate a signal conductor in regions where the signal
conductor has a relatively wider spacing from an adjacent
differential pair. Further, the number of gaps, and/or the length
of those gaps, may be set in proportion to the length of the
differential pair to provide approximately the same length of lossy
material adjacent approximately each differential pair. Such a
configuration, for example, may be more useful to provide a
connector with approximately equal amounts of attenuation in each
differential pair through the connector regardless of the length of
the pair.
[0143] Regardless of the number, types and sizes of the lossy
regions desired, the embodiment of FIG. 9A provides just one
example of construction techniques that may be used to form
multiple regions of lossy material adjacent a signal conductor.
FIG. 9B illustrates an alternative construction technique. In the
embodiment of FIG. 9B, openings in the lossy material that define
separation between lossy regions are formed in the perpendicular
regions.
[0144] Lossy regions 920.sub.1 and 920.sub.2 also include a channel
942 which may be configured to receive a signal conductor, such as
a differential pair. In the embodiment illustrated in FIG. 9B,
lossy regions 920.sub.1 and 920.sub.2 include a parallel region 946
and perpendicular regions 944.sub.1 . . . 944.sub.4. In the
embodiment of FIG. 9B, lossy regions 920.sub.1 and 920.sub.2 are
separated by notches 948.sub.1 and 948.sub.2, which form an opening
between perpendicular regions 944.sub.1 and 944.sub.3 as between
944.sub.2 and 944.sub.4, thereby separating region 920.sub.1 from
region 920.sub.2.
[0145] FIG. 9C illustrates yet another embodiment of lossy material
in which regions are formed. As with the embodiments of FIGS. 9A
and 9B, FIG. 9C shows lossy material configured to form a channel
952. A signal conductor or differential pair may be positioned
within channel 952. The lossy material in the embodiment of FIG. 9C
is divided into regions 920.sub.3 and 920.sub.4. In the embodiment
illustrated, regions 920.sub.3 and 920.sub.4 are separated by an
opening or hole 958 that extends through the parallel region 956 of
the lossy material. In this particular embodiment, hole 958 extends
through the channel 952 of the lossy material. Though one generally
round hole is shown, a hole of any desired size or shape may be
used. The hole may be elongated to form a slot generally along the
center of the channel 952. In other embodiments, a plurality of
holes may be formed along the length of channel 952 in each
segment.
[0146] Regions 920.sub.3 and 920.sub.4 represent two regions that
may be formed along the length of one or more signal conductors
disposed within channel 952. Any number of separate regions may be
formed along the length of the signal conductors within channel
952. Forming openings along the centerline of a channel receiving
signal conductors may be desirable because it contributes to
positioning lossy material generally as pictured in FIG. 7B. For
example, a hole in the floor of a channel of lossy material
surrounding differential pair 340.sub.4 would create a region
relatively free of lossy material between pair 340.sub.4 and ground
conductor 330.sub.8 (FIG. 7B). However, the remaining lossy
material in parallel region 956 and perpendicular regions 954.sub.1
and 954.sub.2 would be generally in the position illustrated for
lossy regions 700.sub.1 and 700.sub.2.
[0147] FIGS. 9A-9C demonstrate that lossy portion 250 may be shaped
to control the amount of loss to signals relative to crosstalk
suppression. As shown, the lossy portion 250 may include lossy
members which form a plurality of channels 932, each for receiving
a differential pair. In one embodiment, the signal conductors
within a column may have different lengths and the lossy regions
250 may be sized and arranged to provide a higher loss per unit
length to shorter conductors than to longer conductors.
[0148] The lossy regions in the FIGS. 9A-9C are formed using a two
shot molding operation. However, regions of lossy material may be
formed in any suitable way. FIGS. 10A and 10B illustrate an
alternative construction technique. In the embodiments of FIGS. 10A
and 10B, the lossy regions may be formed by plating a partially
conductive coating on a substrate, such as the insulative housing.
A lossy material region may be formed by plating a lossy material.
Alternative, a lossy region may be formed by plating a relatively
highly conductive material in a relatively dispersed coating to
provide a coating with a high resistivity. Though other
manufacturing approaches are possible, including by bombarding a
base material with molecules lines to change the loss properties of
the base material.
[0149] FIG. 10A illustrates a portion of a conductive region
forming a channel 1032 in which a differential pair may be
positioned. A lossy region 1020.sub.1 may be formed by applying a
partially conductive coating 1010. Partially conductive coating
1010 may be applied in any suitable way. In the pictured
embodiment, known techniques for plating plastics with metal or
other conducting material may be used.
[0150] Once a partially conductive coating 1010 is applied, lossy
region 1020.sub.1 may be over molded with an insulative material.
Though, in some embodiments, no further processing of a wafer may
be required after a partially conductive coating is applied.
[0151] FIG. 10B illustrates an alternative embodiment. In the
embodiment of FIG. 10B, masking or other suitable manufacturing
technique is used to control the areas coated with partially
conductive coating 1010. In the embodiment of FIG. 10B, structures
to either side of channel 1042 are coated, but the floor of channel
1042 is not coated. As can be seen from FIG. 10B, using a partially
conductive coating may provide greater control over the positioning
of lossy regions.
[0152] Having thus described several aspects of at least one
embodiment of this invention, it is to be appreciated various
alterations, modifications, and improvements will readily occur to
those skilled in the art.
[0153] As one example, a connector designed to carry differential
signals was used to illustrate selective placement of lossy
material to achieve a desired level of crosstalk reduction at an
acceptable level of attenuation to signals. The same approach may
be applied to connectors that carry single-ended signals. Also,
shielding may be provided by capacitively coupling an electrically
lossy member to two structures. Because no direct conducting path
need be provided, it is possible that the electrically lossy
material may be discontinuous, with electrically insulating
material between segments of electrically lossy material.
[0154] Further, although many inventive aspects are shown and
described with reference to a daughter board connector, it should
be appreciated that the present invention is not limited in this
regard, as the inventive concepts may be included in other types of
electrical connectors, such as backplane connectors, cable
connectors, stacking connectors, mezzanine connectors, or chip
sockets.
[0155] As a further example, connectors with four differential
signal pairs in a column were used to illustrate the inventive
concepts. However, the connectors with any desired number of signal
conductors may be used.
[0156] Also, FIG. 3 illustrates perpendicular portions of lossy
material, such as portions 334.sub.1 . . . 334.sub.4, contacting
each ground conductor. However, it is not necessary that each
perpendicular portion contact a ground conductor. Lossy regions
could be coupled to conductors or other lossy regions other than by
direct connection. For example, capacitive coupling could be
employed and a suitable amount of coupling may be provided by
establishing spacing between the lossy material and a ground
conductor that achieves the desired amount of coupling. Further, it
is not a requirement that every ground conductor be coupled to a
perpendicular portion. In some embodiments, there may be no lossy
region adjacent one or more of the ground conductors in a column.
Omitting or reducing the width of perpendicular portions coupled to
some or all of the ground conductors may reduce the amount of
signal attenuation that occurs. Accordingly, the placement and
width of lossy regions may be adjusted to provide a suitable level
of signal attenuation relative to a suitable reduction in
crosstalk, resonances or other anomalies that interfere with signal
propagation.
[0157] Such alterations, modifications, and improvements are
intended to be part of this disclosure, and are intended to be
within the spirit and scope of the invention. Accordingly, the
foregoing description and drawings are by way of example only.
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